for the food had not been touched.  That the motive was not robbery was also plain from the fact that not a drawer had been opened or a lock forced, while the money in his pocket was still intact.  The doctors had certified that the wound could not have been self-inflicted, while there was plenty of evidence to show that there had not been a struggle.  From the fact that the front-door was locked, and that the key was in the murdered man’s pocket, it was certain that the assassin must have left the house by the back.  There was one question, however, so trivial in itself that one might have been excused for not taking note of it, that attracted my attention.  As I have said, the old man had been stabbed from behind, and when he was discovered by the police next day, his overturned chair was lying beside him.  This, to my mind, showed that he had been seated with his back to the door when the crime had been perpetrated.  When I had examined everything else, I turned my attention to the chair.  I did not expect it to tell me anything, yet it was from it that I obtained the clue that was ultimately to lead to the solution of the whole mystery.  The chair was a cheap one, made of white wood, and had the usual smooth strip of wood at the top.  On the back of this piece of wood, a quarter of an inch or so from the bottom, on the left-hand side, was a faint smear of blood.  The presence of the blood set me thinking.  When found, the chair had been exactly eighteen inches from the body.  The mere fact that the man had been stabbed from behind and to the heart, precluded any possibility of his having jumped up and caught at the back of the chair afterwards.  Placing my left hand upon the back, I clasped my fingers under the piece of wood above-mentioned, to discover that a portion of the second finger fell exactly upon the stain.

“Now I think I understand the situation,” I said to myself.  “The old man was seated at the table, about to commence his meal, when the murderer entered very quietly by the door behind him.  He rested his left hand upon the chair to steady himself while he aimed the fatal blow with his right.”

But in that case how did the knife touch the middle finger of his left hand?  From the fact that the body was discovered lying upon its back just as it had fallen, and that the chair was also still upon the floor, it was evident that the blood must have got there before, not after, the crime was committed.  Leaving the room I went out to the yard at the back and studied the paling fence.  The partition which separated the yard from that of the house next door, was old, and in a very dilapidated condition, while that at the bottom was almost new, and was armed at the top with a row of bristling nails.  Bringing the powerful magnifying-glass I had brought with me for such a purpose, to bear upon it, I examined it carefully from end to end.  The result more than justified the labour.  A little more than half way along I discovered another small smear of blood.